Macroevolution and Speciation 4/26/2017 Macroevolution and Speciation Evolution creates (and destroys) new species, but … What is a species? Its not as straightforward a question as most believe. These are members of different species - eastern (left) and western (right) meadowlark. G. Podgorski, Biol. 1010

Thursday, September 19, 2013 Get the handouts from the front Get an iPad if needed You will have 5 minutes to review your document before presenting You will present for no more than 5 minutes Talk about speciation after presentations Vocab Quiz tomorrow BONUS DUE TOMORROW

Thursday, September 19, 2013 Pick up handouts Get with your groups to discuss presentation You’ll have 5 minutes to look over rubric and fix anything Presentations will be 5 minutes each—MAX Speciation talk afterward Vocab quiz 3 tomorrow—time for questions after

What is a Species? There is only one extant (existing) human species. Macroevolution What is a Species? 4/26/2017 There is only one extant (existing) human species. G. Podgorski, Biol. 1010

What is a Species? And these are all members of a single species. Macroevolution What is a Species? 4/26/2017 And these are all members of a single species. G. Podgorski, Biol. 1010

Macroevolution Determining What Is and What Isn’t a Distinct Species Can Have Economic Consequences 4/26/2017 Northern spotted owl (left) and barred owl (right). G. Podgorski, Biol. 1010

Macroevolution 4/26/2017 What is a Species? The definition we’ll use is this: A species is a group of individuals capable of interbreeding to produce fertile offspring. This is the biological species concept. Like all attempts to define a species, it has many problems. G. Podgorski, Biol. 1010

One Problem in the Biological Species Concept Macroevolution 4/26/2017 One Problem in the Biological Species Concept For asexually-reproducing organisms, like these bacteria, what constitutes a species? G. Podgorski, Biol. 1010

…and another problem with the Biological Species Concept… Macroevolution 4/26/2017 …and another problem with the Biological Species Concept… Where do you draw the line between different ‘species’? G. Podgorski, Biol. 1010

What is a population? Members of a species that live in the same geographical area and interbreed

How Many Species Are There? Macroevolution 4/26/2017 How Many Species Are There? We don’t know. About 2 million species have been described. Estimates of existing species number range from 4 million to 100 million (with 10-15 million being a more commonly considered upper estimate). G. Podgorski, Biol. 1010

How did this diversity of life come to be? Macroevolution 4/26/2017 How did this diversity of life come to be? Species = basic unit Continuous lineage - information passed through genes Speciation - rise of new species G. Podgorski, Biol. 1010

Two Patterns of Speciation Macroevolution 4/26/2017 Two Patterns of Speciation Branching evolution can be Adaptive radiation if many species come from one common ancestor G. Podgorski, Biol. 1010

Macroevolution 4/26/2017 How Do Species Arise? The key to speciation is reproductive isolation of populations. There are extrinsic and intrinsic reproductive isolating mechanisms. Geographic isolation is the primary extrinsic reproductive isolating mechanism. G. Podgorski, Biol. 1010

Process of speciation: Macroevolution 4/26/2017 Process of speciation: Parent species 2 separate species III. Don’t interbreed II. Diverge I. Barrier G. Podgorski, Biol. 1010

Reproductive Isolation May Occur With or Without Geographic Isolation Macroevolution 4/26/2017 Reproductive Isolation May Occur With or Without Geographic Isolation Allopatric speciation occurs when geographic isolation creates a reproductive barrier (an extrinsic mechanism). Sympatric speciation occurs when a reproductive barrier is created by something other than geographic isolation (intrinsic mechanisms). G. Podgorski, Biol. 1010

Allopatric Speciation Macroevolution 4/26/2017 Allopatric Speciation Harris’ antelope squirrel White-tailed antelope squirrel Two species of ground squirrel are postulated to have descended from a common ancestral population that was separated by formation of the Grand Canyon. G. Podgorski, Biol. 1010

Macroevolution 4/26/2017 Intrinsic Reproductive Isolating Mechanisms Are Always Required for Speciation Harris’ antelope squirrel White-tailed antelope squirrel Intrinsic mechanisms involve changes to organisms that prevent interbreeding. In allopatric speciation, intrinsic mechanisms come into play once populations are physically separated. In sympatric speciation, intrinsic mechanisms are the only ones involved. G. Podgorski, Biol. 1010

Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation Macroevolution 4/26/2017 Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation (different habits within an overlapping range) G. Podgorski, Biol. 1010

Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation Macroevolution 4/26/2017 Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation Courtship rituals, like these, are critical for mating within a species, but ineffective for attracting members of other species. G. Podgorski, Biol. 1010

Behavioral Isolation Mechanisms Macroevolution 4/26/2017 Behavioral Isolation Mechanisms Courtship rituals, like these, are critical for mating within a species, but ineffective for attracting members of other species. G. Podgorski, Biol. 1010

Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation Macroevolution 4/26/2017 Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation G. Podgorski, Biol. 1010

Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation Macroevolution 4/26/2017 Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation G. Podgorski, Biol. 1010

Hybrid Infertility Was the Impetus for Cloning a Mule Macroevolution 4/26/2017 Hybrid Infertility Was the Impetus for Cloning a Mule G. Podgorski, Biol. 1010

Speciation Occurs at Widely Differing Rates Macroevolution 4/26/2017 Speciation Occurs at Widely Differing Rates A slow rate of speciation evidenced by a living horseshoe crab (13 extant species) and a 300 million year-old fossil species A rapid rate of speciation evidenced by Galapagos finches which have diversified into 13 species within the last 100,000 years. G. Podgorski, Biol. 1010

Macroevolution 4/26/2017 Speciation Rates Generalists, like the horseshoe crab, tend to remain as stable species. Specialists, like the Galapagos finch, tend to be unstable as species. Speciation also becomes rapid when, as occurred with Galapagos finches, new niches become available. G. Podgorski, Biol. 1010

Speciation Dynamics - Gradualism or Punctuated Equilibrium? Macroevolution 4/26/2017 Speciation Dynamics - Gradualism or Punctuated Equilibrium? Punctuated equilibrium appears to be a more accurate view of speciation dynamics. G. Podgorski, Biol. 1010

Does Evolution Create the Perfect Organism? Macroevolution 4/26/2017 Does Evolution Create the Perfect Organism? No, only better organisms as evolution is constrained by history and buffeted by random events. Essentially, every organism on earth is in significant part a sum of accidents. G. Podgorski, Biol. 1010

Macroevolution 4/26/2017 G. Podgorski, Biol. 1010

Macroevolution 4/26/2017 Species Come and Go Best estimates from the fossil record indicate that greater than 99% of species that have exited are now extinct. A typical “lifetime” for a species is about 1 million years. G. Podgorski, Biol. 1010

Mass Extinctions Are a Fact of Life Macroevolution 4/26/2017 Mass Extinctions Are a Fact of Life 90% of all species that have ever existed are now extinct … G. Podgorski, Biol. 1010

Macroevolution 4/26/2017 Gary Larson G. Podgorski, Biol. 1010